The solenoid valve is a well-known device for controlling fluid flow. It invariably consists of a multi-turn conductive coil having an axial passage. A ferro-magnetic valve member is movable axially within the passage toward and away from a valve seat located between an inlet port and an outlet port. The valve member is formed with a sealing surface and is movable between a closed position wherein the sealing surface is seated against the valve seat so as to isolate the inlet and outlet ports and an open position wherein the sealing surface is spaced from the valve seat allowing fluid flow between those ports. Usually, the valve member is biased toward its open or closed position and is moved to the opposite position by the magnetic field produce by the coil when a voltage is applied to the coil. In other words, the valve may be opened or closed when the coil is energized depending upon the initial state of the valve member.
In traditional solenoid valves of this general type, all of the components of the valve form a unitary assembly. In other words, the flow path through the valve is fixed and the valve member is permanently mounted within the coil and is not easily removable. Therefore, if the fluid flow path through the valve has to be sterilized, the entire valve including the coil must be subjected to sterilization.
Also, valves of this type are usually dedicated to a particular instrument or apparatus. To be used in a fluid control application, fluid connections must be made between the valve inlet and outlet ports and other components of the instrument or apparatus, which is time consuming and expensive. Once assembled in the particular instrument or apparatus, the components of the valve cannot be used for any other purpose. That is, all components of the valve are dedicated to that particular application.